Dual gear pumps



April 18, 1967 MASARU YONEl ET AL 3,314,369

DUAL GEAR PUMPS Filed Sept. 15, 1966 PUMP UNIT'I PUMP UNIT 1 l I I3 l4 Fig.5

INVENTORS:

MA SA Ru YONE/ MASATOS/ YASUKA WA United States Patent 3,314,369 DUAL GEAR PUMPS Masaru Yonei, Kohe-shi, and Masatosi Yasukawa, Himejishi, Japan, assignors to Kawasaki Kokuki Kogyo Kabushiki Kaisha, Hyogo-ken, Japan, a corporation of Japan Filed Sept. 15, 1966, Ser. No. 579,725 Claims priority, application Japan, Oct. 5, 1965, 40/ 60,636 Claims. (Cl. 103-126) The present invention relates to precision metering pumps and more particularly to dual gear pumps adapted for use in spinning synthetic filaments and the like.

The metering pumps used in the spinning ofsynthetic filaments, which govern the flow spinning solution to the spinning nozzles for forming individual filaments, are required to be made with great accuracy and are considerably expensive. Additionally, where a separate pump is used for each spinning position, the space to be occupied by said pump becomes relatively large. In view of the foregoing, the so-called dual gear pump has been proposed, for instance, by US. Patent No. 2,533,320 and US. Patent No. 2,818,023, which is of the type wherein two sets of gear pumps are mounted within a single housing and the liquids delivered by the gear pumps are discharged through respective discharge ports. These gear pumps according to said US. patents have heretofore been employed commercially with much success but possess inherent drawbacks.

In the dual gear pump according to US. Patent No. 2,533,320, a middle plate is disposed between two gear pump units. The gear units are arranged in juxtaposed relation and each unit comprises a drive gear and an intermeshed driven gear. The metal plate is used as a common side wall for the pump units and has a passage groove formed therein in a side face that is in contact with the second pump unit which is located at a greater distance from the discharge port in the housing; and this groove is in communication with an axial passage formed in the axis of the driven gear to provide a discharge passage. The groove mentioned above extends radially of the gear over the entire length from the crest of the gear tooth to the axis of the gear. Such being the arrangernent, the liquid leaks along the said face of the gear, resulting in lowering of the volumetric efficiency. An other drawback of this type of dual gear pump is that, since the length of the passage including the aforementioned groove and axial passage in the axis of the gear shaft is considerably long, there is produced a difference between the amount of liquid delivered by the first gear pump, which is positioned closer to the outlet of the housing, and that delivered by the second gear pump, which is positioned further from said outlet. Still another disadvantage of the described prior dual gear pump is that an axial thrust produced by the pressure of the liquid flowing through the aforementioned groove acts on the side face of the gear, which renders the mechanical efficiency of the gear pump lowered and, in some cases, causes wearing or binding of the gear at its side face. Still another drawback is that the solution tends to reside at the edge corner of the aforementioned groove, thus degrading the quality of the resultant filaments.

In the gear pump disclosed in U.S. Patent No. 2,818,-

023, on the other hand, the liquid being delivered by the second gear pump unit, which is located at a greater distance from the discharge port in the housing, is once led to the opposite side of said discharge port in the housing and, after passing through a generally U-shaped passage, is led into an axial passage formed in the axis of the gear. Such an arrangement is disadvantageous in that both gear pump units differ in the amount of liquid respectively delivered, because of the extremely great difference in length between the discharge passages leading from said gear pump units. Another disadvantage of this type of dual gear pump is that, since the aforemen tioned discharge passages have so many flexures and form in sudden expansion and contraction, for instance, the liquid such as molten polymer accumulates at the dead corners of said flexures. The deteriorated solution from these dead corners mixes in with the fresh spinning solution flowing past; accordingly, the quality of the resultant filaments is degraded.

A primary object of the present invention, therefore, is to eliminate the aforementioned drawbacks possessed by the conventional dual gear pumps.

Another object of the invention is to provide a dual gear pump of the type in which the amounts of liquid to be delivered by two gears pump units are the same.

Still another object of the invention is to provide a dual gear pump of the type in which no liquid is permitted to reside in the discharge passages.

Still another object of the invention is to provide a dual gear pump of the type in which gears are not subjected to axial thrust produced by the pressure of the liquid.

These and other objects and advantages of the invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a front elevation of a dual gear pump embodying the present invention;

FIGURE 2 is a cross section taken on the line IIII of FIG. 1;

FIGURE 3 is a cross section taken on the line III-III of FIG. 2; and

FIGURES 4 and 5 respectively illustrate the other embodiments which are shown in cross section taken on the line IVIV of FIG. 3.

Referring to the drawings, the dual gear pump of the present invention comprises a pump unit I consisting of intermeshing gears 1 and 2 and a pump unit II similarly consisting of intermeshing gears 3 and 4, said pump unit I and said pump unit II being arranged with a middle plate 8 interposed therebetween in such a manner that the gears 1 and 3 and gears 2 and 4 are in concentrical relation to each other respectively. The gear units are mounted within respective spaces provided in gear plates 5 and 6 for the accommodation of said gears 1 and 2 and gears 3 and 4 therein in the intermeshing condition, and on the exterior sides of the gear plates 5 and 6 there are positioned side plates 7 and 9 respectively. The gears 1 and 3 are arranged to be driven by a common shaft 10 of these gears extending through the side plate 7, middle plate 8 and the side plate 9 and journaled in said plates by way of bushings 17, said gears 1 and 3 being secured to said common shaft 10 by means of keys 16. Gears 2 and 4 are rotatably mounted on a common shaft 11 which is inserted into the side plate 7, middle plate 8 and side plate 9, and is further fixed by pressing to middle plate 8 that the liquid may not leak from the contacting face between common shaft 11 and middle plate 8. The plates 5, 6, 7, 8 and 9 may be held together by bolts or the like without using a packing since they are finished flat with high precision.

Referring to FIG. 2, the left hand end of the pump assembly is the discharge side and the discharge passage for the pump unit I is bored in the side plate 7. This passage is shown in FIGS. 4 and 5 by reference numeral 14, though not clearly shown in FIG. 2.

The discharge passage for the pump unit II is composed of an axial passage 13 formed in the shaft 11 from the left hand end in FIG. 2 to substantially the middle portion thereof and a passage 12 formed in said shaft 11 and the middle plate 8. Passage 12 communicates the right hand end of the passage 13., An embodiment of this passage .is clearly shown in FIG. 4' wherein the passage 13 is connected with the discharge port of the pump unit II by way of the passage 12 formed slantingly in the shaft 11 and middle plate 8. FIG. 5 shows another embodiment of the passage 12. In'this embodiment, the passage 12 is extending from the inner end of the passage 13 substantially at right angles to said passage 13 radially of the shaft 11 to proceed into the middle plate 8 and thence extending in said middle plate 8 slantingly to reach thedischarge port of the pump unit II.

Indicated at 15 in FIGS. 1 and 3 is an intake port for the liquid.

As is clear from the foregoing description, in the pump assembly of the presentinvention in which the discharge passage for the pump unit II does not include a groove formed in a side face of the middle plate 8, the gear is not subjected to axial thrust and additionally, since the passage does not include a sharp flexure and the crosssection thereof does not vary suddenly, the possibility of the discharge liquid accumulating is reduced remarkably. Furthermore, the length of the discharge passage for the pump unit II can be rendered extremely short due to the fact that the passage 13 is connected with the discharge port of the pump unit II by the passage 12 along the shortest path, so that the difference between the amounts of liquid being discharged by the pump units I and II can be rendered small.

Even with the discharge passage arranged in the manner described, however, there still remains a difference between the flow resistances in the discharge passages for both pump units since the lengths of said passages are different. Therefore, in order to make the final discharge pressures of both pump units, i.e. the pressures of liquid at the spinnerets, equal, it is necessary to make the pressure at the discharge port of the longer discharge passage, i.e. the discharge port of the pump unit II, higher than that of the pump unit I. This, however, would cause a difference between the amounts of liquid leaking .from the pump units I and II, providing a cause of difference between the amounts of liquid to be discharged by said two units.

According to the present invention, this drawback has been eliminated essentially completely by setting the side clearances of the gears of the pump units I and II at difference values corresponding to the pressure difference at the discharge ports thereof.

Leakage from side gap is represented by theoretical formula wherein q stands for amount of leakage; P for pressure, S for gap; s for viscosity of liquid; and K for leakage coefficient. a 7 7 Inorder to make equal the amounts of leakage through the respective side clearances in the pump units I and II, therefore, the following equation must be established:

wherein P represents the pressure at the entrance or right hand end of passage 14 for the pump unit I; P the pressure at the entrance or right hand end of passage 12 for the pump unit II; S; the gear side clearance of the pump unit I and S the gear side clearance of the pump unit II.

It will be appreciated from the foregoing equation that the discharge amounts of both pump units may be maintained substantially equal by establishing the relationship between the side clearances S and S of the pump units I and II so as to satisfy the equation a Fa/E E in accordance with the values of the discharge pressure P; and'P thereof.

What is claimed is:

1. A dual gear pump comprising a first pump unit consisting of a pair of inter-meshing gears and a gear plate provided with a space therein for accommodating said gears in the intermeshing condition, and having a discharge port; a second pump unit consisting of a pair of intermeshing gears and a gear plate provided with a space therein for accommodating said gears in the intermeshing condition, and having a discharge port; a middle plate arranged between said first and second pump units; a pair of side plates arranged on the exterior faces of said first and second pump units; a common drive shaft connected toone of the gears of said first pump unit and one of the gears of said second pump unit for driving the same; means to rotatably support said drive shaft in said pair of side plates and said middle plate; a common support shaft retained in said pair of side plates and said middle plate for rotatably supporting the other'gear of said first pump unit and therother gear of said second pump unit; a discharge passage for said first'pump unit extending from said discharge port of said first pump unit across said side plate adjacent to said pump unit; and a discharge passage for said second pump unit composed of an axial passage formed in said common support shaft from the end thereof closer to the side plate adjacent to said first pump unit and extending to substantially the;

middle of said shaft and a passage formed interior of-said common support shaft and said middle plate for communicating the inner end of said axial passage with said discharge port of said second unit.

2. A dual gear pump as defined in claim 1, wherein said passage that communicates the inner end of the axial passage in said common support shaft with the discharge port of said second pump unit, extends interior of said common support shaft and said middle plate slantingly from said inner end' to said discharge port.

3. A dual gear pump as defined in claim 1, wherein;

said passage that communicates the inner end of the axial passage insaid common support shaft with the discharge port of said second pump unit, extends from the inner end of said common support shaft'to proceed into said middle plate and thence extending further slantingly V to reachsaid discharge port. a

4. A dual gear pump as defined in claim 1, wherein the relationship between the sideclearances of said first and second pump units. is established in accordance with the liquid pressure at the entrance of passage for each. pump unit so as to satisfy the equation SI/SII=3\/E/F;

pump unit, each having a driving gear meshing with a driven gear; mounting means for each unit having a discharge port and being provided with space for accommodating said meshed gears; a plate disposed between said pump units, and side plates arranged on the exterior ends of said pump units; a common shaft rotatably supporting the driven gears of said first and second pump units; a discharge passage for said first pump unit ex tending from the discharge port thereof through the side plate adjacent thereto; and a discharge passage for said second pump unit comprising an axial passage through said common support shaft and a passage formed interior of said common support shaft and the plate between said pump units which opens at the discharge port of said second pump unit.

References Cited by the Examiner UNITED STATES PATENTS 2,207,493 7/1940 Van Dartelen 103-126 2,481,143 9/1949 Muller 103126 2,533,320 12/1950 Hull et a1. 103126 2,685,839 8/1954 Vandenburgh 103-126 2,818,023 12/1957 Lundstrom 103-126 DONLEY J. STOCKING, Primary Examiner. W. J. GOODLIN, Assistant Examiner. 

1. A DUAL GEAR PUMP COMPRISING A FIRST PUMP UNIT CONSISTING OF A PAIR OF INTERMESHING GEARS AND A GEAR PLATE PROVIDED WITH A SPACE THEREIN FOR ACCOMMODATING SAID GEARS IN THE INTERMESHING CONDITION, AND HAVING A DISCHARGE PORT; A SECOND PUMP UNIT CONSISTING OF A PAIR OF INTERMESHING GEARS AND A GEAR PLATE PROVIDED WITH A SPACE THEREIN FOR ACCOMMODATING SAID GEARS IN THE INTERMESHING CONDITION, AND HAVING A DISCHARGE PORT; A MIDDLE PLATE ARRANGED BETWEEN SAID FIRST AND SECOND PUMP UNITS; A PAIR OF SIDE PLATES ARRANGED ON THE EXTERIOR FACES OF SAID FIRST AND SECOND PUMP UNITS; A COMMON DRIVE SHAFT CONNECTED TO ONE OF THE GEARS OF SAID FIRST PUMP UNIT AND ONE OF THE GEARS OF SAID SECOND PUMP UNIT FOR DRIVING THE SAME; MEANS TO ROTATABLY SUPPORT SAID DRIVE SHAFT IN SAID PAIR OF SIDE PLATES AND SAID MIDDLE PLATE; A COMMON SUPPORT SHAFT RETAINED IN SAID PAIR OF SIDE PLATES AND SAID MIDDLE PLATE FOR ROTATABLY SUPPORTING THE OTHER GEAR OF SAID FIRST PUMP UNIT AND THE OTHER GEAR OF SAID SECOND PUMP UNIT; A DISCHARGE PASSAGE FOR SAID FIRST PUMP UNIT EXTENDING FROM SAID DISCHARGE PORT OF SAID FIRST PUMP UNIT ACROSS SAID SIDE PLATE ADJACENT TO SAID PUMP UNIT; AND A DISCHARGE PASSAGE FOR SAID SECOND PUMP UNIT COMPOSED OF AN AXIAL PASSAGE FORMED IN SAID COMMON SUPPORT SHAFT FROM THE END THEREOF CLOSER TO THE SIDE PLATE ADJACENT TO SAID FIRST PUMP UNIT AND EXTENDING TO SUBSTANTIALLY THE MIDDLE OF SAID SHAFT AND A PASSAGE FORMED INTERIOR OF SAID COMMON SUPPORT SHAFT AND SAID MIDDLE PLATE FOR COMMUNICATING THE INNER END OF SAID AXIAL PASSAGE WITH SAID DISCHARGE PORT SAID SECOND UNIT. 